The present invention pertains to a modified pipe inlet for improving flow through a pipe, such as a liner for repairing a failing culvert.
Culvert lining systems are designed as a solution for repairing failing culverts without requiring removal of existing pipe by excavation. Since much of the highway system in the United States was built in the 1950s, culverts built under the roads were often made of either corrugated metal or concrete, which each have a design life of 45-50 years. Repairing such culverts before they enter a critical state of collapse is important for the continuing safety of the road above.
To repair a failing culvert, one common technique is to install a liner inside of the culvert. For example, and referring now to FIG. 1, when the culvert is in the form of a corrugated metal pipe 10, a liner 20 of a slightly smaller diameter can be inserted into and installed in the pipe 10. ISCO Industries, LLC, the assignee of the present application, markets and describes one such culvert lining system for repairing failing culverts under the SnapTite® trademark. In the SnapTite® Culvert Lining System, the liner 20 is generally comprised of a continuous wall defining an inner wall surface and an exterior wall surface, and further defining a central fluid passageway extending from an inlet end to an outlet end. In many applications, the liner 20 is cylindrical and has a circular cross-section, but in some applications, the liner 20 may have an elliptical cross-section. In any event, once the liner 20 has been installed, a grout mixture 30 is packed into the annular space between the pipe 10 and the liner 20. Grouting of the annular space is important not only in securing the liner 20 relative to the pipe 10, but also helps to stabilize the surrounding soil and minimizes the potential for settlement or collapse of the road. The grout mixture 30 also provides additional support to the pipe 10 and increases the collapse strength of the liner 20.
Referring now to FIG. 2, once the liner 20 has been installed, the flow capacity of the rehabilitated culvert is equal to or better than that of the failing culvert in a low-flow condition.
Referring now to FIG. 3, in a heavy storm or other full-flow event, when the liner 20 is full of fast-flowing water, turbulence creates small eddies or countercurrents just inside of the inlet. This turbulence actually constricts the flow of the influent, reducing the effective diameter of the liner 20 and the flow capacity at this location. This reduction in the effective diameter is typically referred to as a vena contracta, i.e., the point in a fluid stream where the diameter of the stream is minimized.
The flow rate can be modified to some extent by altering the inlet or outlet conditions in the culvert. In most cases, the outlet conditions are difficult to alter. The focus thus shifts to altering the inlet conditions.
In most current constructions, such as in the SnapTite® Culvert Lining System described above, the inner diameter of the liner is substantially constant along the length of the liner. In other words, there is no curvature or contour at or near the inlet end of the liner, nor any curvature or contour anywhere along the length of the liner.
In some pipe constructions, a curvature may be provided at the inlet end in an effort to reduce head losses. For example, U.S. Patent Publication No. 2005/0229982 describes a device that is “force fit into opening 32 of a pipe . . . and extends from neck 52 to lip 51, thereby defining a fluid passage having a rounded, gradually curving mouth 54.” See Paragraphs [0030]-[0031].
Nonetheless, there still remains a need for a modified pipe inlet that would minimize any constriction and improve flow through a pipe, such as a liner for repairing a failing culvert.